If you need to make custom spacers for standoffs, for whatever reason, I suggest using PVC tubing. The same stuff used for water cooling but some that just barely fits over the bolts you want to use for mounting. Just cut it to the length you need to position the board. I used it in a case that had these weird metal tabs instead of standoffs; the things were useless and I wanted to replace them. The end product was solid but it was a lot more work than I thought so not worth it unless you really need custom standoffs.

__________________He either fears his fate too much, or his deserts are small, that dares not put it to the touch, to gain or lose it all.
- James Graham